The present invention relates to semiconductor transducers and more particularly, to a leadless transducer having a metal media protected member, whereby pressure is applied to the metal member and transmitted to the leadless transducer.
Semiconductor pressure transducers are frequently used in applications which require operation in harsh environments that are corrosive and/or involve high temperature. Accordingly, the stress-sensing network of transducers used in such applications must be protected from these harsh environmental conditions in some way in order for the transducer to remain operational over extended periods of time. In the past, surface overcoatings such as silicon nitride, silicon dioxide and the like, have been provided over the stress-sensing network for protection from harsh operating environments.
In any event, a new device or class of sensors has been developed and is referred to by the assignee herein as xe2x80x9cleadless sensorsxe2x80x9d. Reference is made to U.S. Pat. No. 5,973,590 entitled, xe2x80x9cUltra Thin Surface Mount Wafer Sensor Structures and Methods for Fabricating the Samexe2x80x9d which issued on Oct. 26, 1999 to A. D. Kurtz et al. and is assigned to the assignee here, Kulite Semiconductor Products, Inc. That patent describes a leadless sensor which involves an improved method for hermetically sealing a semiconductor pressure transducer and for providing superior operating characteristics. A hermetically sealed sensor, according to the above-noted patent, which is incorporated herein by reference, is formed by fusion-bonding a P+ sensor network, P+ fingers which also contain contact areas and a P+ rim to an oxide coated diaphragm wafer and then electrostatically bonding a piece of glass having apertures smaller than the fingers which line up with the contact regions on the sensor. The diaphragm wafer is formed to provide a series of flexible diaphragm structures underneath the sensor network and the glass wafer has a series of depressions on the side that is sealed to the P+ fingers and rim such that the sensor network will not seal to the glass and of a sufficient depth to allow the diaphragm to deflect. Many different embodiments of the structure have been shown in the above-noted patent and other patents which are related thereto.
In any event, such a leadless sensor exhibits superior protective operation compared to prior art sensors, but still require, for certain applications, greater protection. For example, prior art transducers have been employed in many different environments that subject the transducer to stringent operating conditions, such as high temperature and high pressure. Such transducers have been used in the automotive field to monitor engine pressure, coolant pressure and so on. They are used in the aircraft field to measure aerodynamic pressures and in many other varied fields, where high pressure and temperatures are a concern. Apart from the high operating temperatures and pressures, the transducers have been subject to various pollutants and gasses which are present in such environments. Therefore, even though the leadless transducer is hermetically sealed and protected, it still can be compromised by a highly corrosive environment. Therefore, the present invention describes a leadless transducer which is protected by a metal diaphragm structure attached to the housing. The metal diaphragm structure is shaped so that a center boss portion of the metal diaphragm co-acts with the boss on the leadless transducer to apply a force thereto. The metal diaphragm structure operates to enclose the leadless sensor and prevents the sensor from being exposed to a harsh environment. See U.S. Pat. No. 5,587,601 entitled, xe2x80x9cSupport Structure for a Semiconductor Pressure Transducerxe2x80x9d which issued on Dec. 24, 1996 to A. D. Kurtz and is assigned to the assignee herein. This patent shows metal structures operating with sensors.
A pressure sensor comprises a first cylindrical metal member which has a closed top surface and an opened bottom surface, the closed top surface has a central boss extending towards the open bottom surface, and a second cylindrical metal member has an inner recess surrounded by a flange, with the outer surface of the second cylindrical member secured to the periphery about the open bottom surface of the first metal member. A leadless semiconductor sensor has a central boss surrounded by an active deflecting region to enable the sensor to produce an output when a pressure is applied to the boss, the sensor is positioned on an insulator support member and located in the inner recess of the second cylindrical member with the insulator support member positioned on the flange, with the central boss of the sensor in contact with the central boss of the first cylindrical metal member to cause a force applied to the closed top surface of the first cylindrical member to be applied to the sensor via the associated bosses.